You can only achieve a good master by using analogue equipment

Many others would strongly disagree. There's a wealth of incredible digital tools available today but it really comes down to who is using the tools rather than the tools themselves.

A good mastering engineer will use whatever tools they see as fit for the job.That could be digital, analogue or a combination of both. All that matters is that the engineer uses their experience and knowledge, implementing the tools wisely to achieve the desired result, and that the engineer knows the characteristics of their tools well enough to choose what process is right for a particular task.